Transdisciplinary Program to Identify Novel Antifungal Targets This Program Project represents a unique, coordinated and synergistic strategy to discover novel antifungal drugs to effectively treat life-threatening invasive fungal infections. Invasive fungal infections remain a leading cause of death in the growing population of immunosuppressed patients. Presently, there are several classes of approved antifungal agents, but they suffer from limited clinical efficacy, reduced fungicidal activity in the host, debilitating toxicity profiles, and/or emergence of resistance. To identify innovative antifungal targets and agents, we have merged the disciplines of structural biology, molecular mycology, and vertebrate pathology with our clinical insights and experience to produce a novel direction for antifungal development. This focus targets three cell signaling pathways critical to the capability of pathogenic fungi to survive and grow at human body temperature (37C). Our previous studies have identified and carefully validated these signal transduction circuits that enable high temperature growth at 37C and virulence for the three major fungal pathogens (Candida, Aspergillus, Cryptococcus). These three pathways are: (1) the calcineurin pathway, a conserved pathway for fungal virulence; (2) the Ras pathway, which governs fungal morphogenesis and stress responses; and (3) the trehalose pathway, which synthesizes a fungal specific thermoprotective carbohydrate and other stress protectants. Our work to date has also identified key interconnections among these pathways, which we will further investigate for synergistic therapeutic potential. Our overall hypothesis is that by applying structural biologc approaches to rigorous investigations in mycology, we will define critical, targetable differences between key fungal proteins required for thermotolerance and the proteins' mammalian counterparts, creating a therapeutic platform on which to develop novel fungal-specific inhibitors that lack mammalian cross-reactivity. Our overall aims are to: (1) define fungal-specific structural differences in the three signaling pathways, (2) generate novel inhibitors against these signaling pathways and optimize their entry into fungal cells, and (3) test inhibitors for in vitro and in vivo biological activity. To accomplish these Aims, we propose three linked Projects and three supporting Cores. The impact of this novel approach will be to identify and validate potent fungal-specific inhibitors of these critical signaling pathways that can be further translated for clinical application by our industry collaborators to drugs to improve patient outcome.